package com.hit.basmath.learn.others;

/**
 * 392. Is Subsequence
 * <p>
 * Given a string s and a string t, check if s is subsequence of t.
 * <p>
 * You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).
 * <p>
 * A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, "ace" is a subsequence of "abcde" while "aec" is not).
 * <p>
 * Example 1:
 * <p>
 * s = "abc", t = "ahbgdc"
 * <p>
 * Return true.
 * <p>
 * Example 2:
 * <p>
 * s = "axc", t = "ahbgdc"
 * <p>
 * Return false.
 * <p>
 * Follow up:
 * If there are lots of incoming S, say S1, S2, ... , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?
 */
public class _392 {
    public boolean isSubsequence(String s, String t) {
        if (s.length() == 0) return true;
        int indexS = 0, indexT = 0;
        while (indexT < t.length()) {
            if (t.charAt(indexT) == s.charAt(indexS)) {
                indexS++;
                if (indexS == s.length()) return true;
            }
            indexT++;
        }
        return false;
    }
}
